FIG. 14 shows a prior art solar cell which is disclosed in "Solar Photovoltaic Power Generation" by Kiyoshi Takahashi, Yoshihiro Hamakawa, and Akio Ushirokawa, Morikita Shuppan, 1980, pages 147, 322, and 323. As shown in the figure, an n.sup.+ layer 2 is disposed at a first surface of a p-type silicon substrate 1, and a collection electrode 4 is disposed on the n.sup.+ layer 2. The collection electrode 4 includes an external connection bus electrode 4a and comb-type bar electrodes 4b and functions as a negative electrode. Where the collection electrode 4 on the n.sup.+ layer 2 is absent, a reflection preventing film 3 is disposed. A plane electrode 5, which functions as a plus side electrode, is disposed on the other surface of the p-type silicon substrate 1.
FIG. 15 shows a solar cell module in which the solar cells 10 as described above are connected serially and in parallel to generate higher power. As shown in the figure, the collection electrode 4 (bus electrode 4a) of one of the two adjacent solar cells 10 is connected with the planar electrode 5 of the other of the cells 10 via a metal foil 6 several tens of microns thick.
A silver foil is usually used as the metal foil 6 and is bent at two location as shown in FIG. 15. One end of the metal foil 6 is welded or soldered to the bus electrode 4a of the collection electrode 4 of the respective solar cells 10. Next, the solar cells 10, having the metal foil 6 connected with the bus electrodes 4a, are arranged upside-down. Thereafter, the free end of each of the metal foils 6 is welded or soldered to the planar electrodes 5 of the adjacent solar cells.
The solar cells 10 connected in series by metal foils 6 are encapsulated in a transparent water-proof resin 7 and the transparent water-proof resin 7 is disposed between glass plates 8. Finally, in an environment where the intrusion of air is prevented, the device is heated above the softening point of the resin so that the solar cells 10, the transparent water-proof resin 7, and the glass plates 8 are adhered. Then, edges of the adhered device are mounted in a metal frame 9, thereby completing a solar cell module.
In such a prior art solar cell, the collection electrode 4 at the surface of one of the adjacent solar cells and the plane electrode 5 at the rear surface of the other of the adjacent solar cells have to be connected by the metal foil 6. The connection process using the metal foil 6 is troublesome because the foil has to be connected at both the front and rear surfaces of the solar cells. Since the collection electrode 4 projects from the front surface, when the metal foil 6 is bonded onto the planar electrode 5 (the respective solar cells are then upside-down), the respective solar cells 20 are unstable. The solar cells are then supported only by the collection electrode 4, thereby making it impossible to apply sufficient force for bonding the metal foil 6 onto the planar electrodes 5.